6u9p

Wild-type MthK pore in ~150 mM K+Wild-type MthK pore in ~150 mM K+

Structural highlights 6u9p is a 1 chain structure with sequence from Methanothermobacter thermautotrophicus. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 1.65Å Ligands: , Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function MTHK_METTH Calcium-gated potassium channel. Publication Abstract from PubMed Potassium channels can become nonconducting via inactivation at a gate inside the highly conserved selectivity filter (SF) region near the extracellular side of the membrane. In certain ligand-gated channels, such as BK channels and MthK, a Ca(2+)-activated K(+) channel from Methanobacterium thermoautotrophicum, the SF has been proposed to play a role in opening and closing rather than inactivation, although the underlying conformational changes are unknown. Using X-ray crystallography, identical conductive MthK structures were obtained in wide-ranging K(+) concentrations (6 to 150 mM), unlike KcsA, whose SF collapses at low permeant ion concentrations. Surprisingly, three of the SF's four binding sites remained almost fully occupied throughout this range, indicating high affinities (likely submillimolar), while only the central S2 site titrated, losing its ion at 6 mM, indicating low K(+) affinity ( approximately 50 mM). Molecular simulations showed that the MthK SF can also collapse in the absence of K(+), similar to KcsA, but that even a single K(+) binding at any of the SF sites, except S4, can rescue the conductive state. The uneven titration across binding sites differs from KcsA, where SF sites display a uniform decrease in occupancy with K(+) concentration, in the low millimolar range, leading to SF collapse. We found that ions were disfavored in MthK's S2 site due to weaker coordination by carbonyl groups, arising from different interactions with the pore helix and water behind the SF. We conclude that these differences in interactions endow the seemingly identical SFs of KcsA and MthK with strikingly different inactivating phenotypes. Selectivity filter ion binding affinity determines inactivation in a potassium channel.,Boiteux C, Posson DJ, Allen TW, Nimigean CM Proc Natl Acad Sci U S A. 2020 Nov 5. pii: 2009624117. doi:, 10.1073/pnas.2009624117. PMID:33154158 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Potassium channel 3D structures

spinqualitylabelsall models 6u9p, resolution 1.65Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image